Effect of cathode collector copper inserts on the hall-heroult cell MHD stability

Abstract

A composite cathode design with copper inserts could reduce the voltage drop and the horizontal currents in the liquid aluminium, which are responsible for the MHD wave instability and the intense metal circulation. A model incorporating full 3d busbar configuration coupled to the electric current in the liquid is used to study the MHD response when the copper inserts are included in the cathode construction. The results confirm the reduction of electric current component in liquid metal along the collector bar direction, however show the equally important horizontal current in the metal pad in the long direction of the cell due to the current distribution over the outgoing collectors. The time dependent MHD solution is applied to industrial cells incorporating the composite cathode, variable bottom and the full neighbor cell network effect. Examples of two types of cells show the possibility for different scenarios: Either decreasing or increasing the MHD stability depending on the overall cell design and operating conditions.